class Compiler {
  constructor(vm) {
    this.el = vm.$el;
    this.vm = vm;
    this.compile(this.el);
  }
  //编译模板，处理文本节点和元素节点
  compile(el) {
    let childNodes = el.childNodes;
    Array.from(childNodes).forEach((node) => {
      if (this.isTextNode(node)) {
        this.compileText(node);
      } else if (this.isElementNode(node)) {
        this.compileElement(node);
      }
      //判断是否有子节点
      if (node.childNodes && node.childNodes.length) {
        this.compile(node);
      }
    });
  }
  //编译元素节点，处理指令
  compileElement(node) {
    //   console.log(node.attributes)
    Array.from(node.attributes).forEach((attr) => {
      let attrName = attr.name;
      if (this.isDirective(attrName)) {
        attrName = attrName.substr(2);
        let key = attr.value;
        this.update(node, key, attrName);
      }
    });
  }
  update(node, key, attrName) {
    let updateFn = this[attrName + "Updater"];
    updateFn && updateFn.call(this,node, this.vm[key],key);
  }
  textUpdater(node, value,key) {
    node.textContent = value;
    new Watcher(this.vm,key,(newValue) => {
        node.textContent = newValue
    })
  }
  modelUpdater(node, value,key) {
    node.value = value;
    new Watcher(this.vm,key,(newValue) => {
        node.value = newValue
    })
    //双向绑定
    node.addEventListener('input',() => {
        this.vm[key] = node.value
    })
  }
  //编译文本节点，处理插值表达式
  compileText(node) {
    //   console.dir(node)
    //{{ msg }}
    let reg = /\{\{(.+?)\}\}/;
    let value = node.textContent;
    if (reg.test(value)) {
      let key = RegExp.$1.trim();
      node.textContent = value.replace(reg, this.vm[key]);

      //创建watcher对象，更新视图
      new Watcher(this.vm, key,(newValue) => {
        node.textContent = newValue
      })
    }
  }
  //判断元素属性是否是指令
  isDirective(attrName) {
    return attrName.startsWith("v-");
  }
  isTextNode(node) {
    //判断是否是文本节点
    return node.nodeType === 3;
  }
  //判断是否是元素节点
  isElementNode(node) {
    return node.nodeType === 1;
  }
}
